[PATCH] spinlock.h cleanup

 - cleanup #defines: I do not follow the rationale behind the
   odd line-wrapped defines at the beginning of the file.  If
   we have to use multiple lines, then we might as well do so
   cleanly and according to normal practice...

 - Remove a level of indirection: do not have spin_lock_foo
   use spin_lock - just explicitly call what is needed.

 - we do not need to define the spin_lock functions twice, once
   for CONFIG_PREEMPT and once for !CONFIG_PREEMPT.  Defining
   them once with the preempt macros will optimize away fine.

 - cleanup preempt.h too

 - other misc. cleanup, improved comments, reordering, etc.

include/linux/preempt.h

 #ifndef __LINUX_PREEMPT_H
 #define __LINUX_PREEMPT_H
 
+/*
+ * include/linux/preempt.h - macros for accessing and manipulating
+ * preempt_count (used for kernel preemption, interrupt count, etc.)
+ */
+
 #include <linux/config.h>
 
 #define preempt_count()	(current_thread_info()->preempt_count)
@@ -31,17 +36,16 @@ do { \
 	barrier(); \
 } while (0)
 
-#define preempt_enable() \
+#define preempt_check_resched() \
 do { \
-	preempt_enable_no_resched(); \
 	if (unlikely(test_thread_flag(TIF_NEED_RESCHED))) \
 		preempt_schedule(); \
 } while (0)
 
-#define preempt_check_resched() \
+#define preempt_enable() \
 do { \
-	if (unlikely(test_thread_flag(TIF_NEED_RESCHED))) \
-		preempt_schedule(); \
+	preempt_enable_no_resched(); \
+	preempt_check_resched(); \
 } while (0)
 
 #define inc_preempt_count_non_preempt()	do { } while (0)
@@ -50,7 +54,7 @@ do { \
 #else
 
 #define preempt_disable()		do { } while (0)
-#define preempt_enable_no_resched()	do {} while(0)
+#define preempt_enable_no_resched()	do { } while (0)
 #define preempt_enable()		do { } while (0)
 #define preempt_check_resched()		do { } while (0)
 

include/linux/spinlock.h

 #ifndef __LINUX_SPINLOCK_H
 #define __LINUX_SPINLOCK_H
 
+/*
+ * include/linux/spinlock.h - generic locking declarations
+ */
+
 #include <linux/config.h>
 #include <linux/preempt.h>
 #include <linux/linkage.h>
 #include <linux/compiler.h>
 #include <linux/thread_info.h>
 #include <linux/kernel.h>
+#include <linux/stringify.h>
 
 #include <asm/system.h>
 
 /*
- * These are the generic versions of the spinlocks and read-write
- * locks..
+ * Must define these before including other files, inline functions need them
  */
-#define spin_lock_irqsave(lock, flags)		do { local_irq_save(flags);       spin_lock(lock); } while (0)
-#define spin_lock_irq(lock)			do { local_irq_disable();         spin_lock(lock); } while (0)
-#define spin_lock_bh(lock)			do { local_bh_disable();          spin_lock(lock); } while (0)
-
-#define read_lock_irqsave(lock, flags)		do { local_irq_save(flags);       read_lock(lock); } while (0)
-#define read_lock_irq(lock)			do { local_irq_disable();         read_lock(lock); } while (0)
-#define read_lock_bh(lock)			do { local_bh_disable();          read_lock(lock); } while (0)
-
-#define write_lock_irqsave(lock, flags)		do { local_irq_save(flags);      write_lock(lock); } while (0)
-#define write_lock_irq(lock)			do { local_irq_disable();        write_lock(lock); } while (0)
-#define write_lock_bh(lock)			do { local_bh_disable();         write_lock(lock); } while (0)
-
-#define spin_unlock_irqrestore(lock, flags)	do { _raw_spin_unlock(lock);  local_irq_restore(flags); preempt_enable(); } while (0)
-#define _raw_spin_unlock_irqrestore(lock, flags) do { _raw_spin_unlock(lock);  local_irq_restore(flags); } while (0)
-#define spin_unlock_irq(lock)			do { _raw_spin_unlock(lock);  local_irq_enable(); preempt_enable();       } while (0)
-#define spin_unlock_bh(lock)			do { spin_unlock(lock); local_bh_enable(); } while (0)
-
-#define read_unlock_irqrestore(lock, flags)	do { _raw_read_unlock(lock);  local_irq_restore(flags); preempt_enable(); } while (0)
-#define read_unlock_irq(lock)			do { _raw_read_unlock(lock);  local_irq_enable(); preempt_enable(); } while (0)
-#define read_unlock_bh(lock)			do { read_unlock(lock);  local_bh_enable();        } while (0)
-
-#define write_unlock_irqrestore(lock, flags)	do { _raw_write_unlock(lock); local_irq_restore(flags); preempt_enable(); } while (0)
-#define write_unlock_irq(lock)			do { _raw_write_unlock(lock); local_irq_enable(); preempt_enable();       } while (0)
-#define write_unlock_bh(lock)			do { write_unlock(lock); local_bh_enable();        } while (0)
-#define spin_trylock_bh(lock)			({ int __r; local_bh_disable();\
-						__r = spin_trylock(lock);      \
-						if (!__r) local_bh_enable();   \
-						__r; })
-
-/* Must define these before including other files, inline functions need them */
-
-#include <linux/stringify.h>
-
 #define LOCK_SECTION_NAME			\
 	".text.lock." __stringify(KBUILD_BASENAME)
 
@@ -60,11 +31,17 @@
 #define LOCK_SECTION_END			\
 	".previous\n\t"
 
+/*
+ * If CONFIG_SMP is set, pull in the _raw_* definitions
+ */
 #ifdef CONFIG_SMP
 #include <asm/spinlock.h>
 
-#elif !defined(spin_lock_init) /* !SMP and spin_lock_init not previously
-                                  defined (e.g. by including asm/spinlock.h */
+/*
+ * !CONFIG_SMP and spin_lock_init not previously defined
+ * (e.g. by including include/asm/spinlock.h)
+ */
+#elif !defined(spin_lock_init)
 
 #ifndef CONFIG_PREEMPT
 # define atomic_dec_and_lock(atomic,lock) atomic_dec_and_test(atomic)
@@ -72,55 +49,42 @@
 #endif
 
 /*
- * Your basic spinlocks, allowing only a single CPU anywhere
- *
- * Most gcc versions have a nasty bug with empty initializers.
+ * gcc versions before ~2.95 have a nasty bug with empty initializers.
  */
 #if (__GNUC__ > 2)
   typedef struct { } spinlock_t;
-# define SPIN_LOCK_UNLOCKED (spinlock_t) { }
+  typedef struct { } rwlock_t;
+  #define SPIN_LOCK_UNLOCKED (spinlock_t) { }
+  #define RW_LOCK_UNLOCKED (rwlock_t) { }
 #else
   typedef struct { int gcc_is_buggy; } spinlock_t;
-# define SPIN_LOCK_UNLOCKED (spinlock_t) { 0 }
+  typedef struct { int gcc_is_buggy; } rwlock_t;
+  #define SPIN_LOCK_UNLOCKED (spinlock_t) { 0 }
+  #define RW_LOCK_UNLOCKED (rwlock_t) { 0 }
 #endif
 
+/*
+ * If CONFIG_SMP is unset, declare the _raw_* definitions as nops
+ */
 #define spin_lock_init(lock)	do { (void)(lock); } while(0)
-#define _raw_spin_lock(lock)	(void)(lock) /* Not "unused variable". */
+#define _raw_spin_lock(lock)	(void)(lock)
 #define spin_is_locked(lock)	((void)(lock), 0)
 #define _raw_spin_trylock(lock)	((void)(lock), 1)
 #define spin_unlock_wait(lock)	do { (void)(lock); } while(0)
 #define _raw_spin_unlock(lock)	do { (void)(lock); } while(0)
-
-/*
- * Read-write spinlocks, allowing multiple readers
- * but only one writer.
- *
- * NOTE! it is quite common to have readers in interrupts
- * but no interrupt writers. For those circumstances we
- * can "mix" irq-safe locks - any writer needs to get a
- * irq-safe write-lock, but readers can get non-irqsafe
- * read-locks.
- *
- * Most gcc versions have a nasty bug with empty initializers.
- */
-#if (__GNUC__ > 2)
-  typedef struct { } rwlock_t;
-  #define RW_LOCK_UNLOCKED (rwlock_t) { }
-#else
-  typedef struct { int gcc_is_buggy; } rwlock_t;
-  #define RW_LOCK_UNLOCKED (rwlock_t) { 0 }
-#endif
-
 #define rwlock_init(lock)	do { } while(0)
-#define _raw_read_lock(lock)	(void)(lock) /* Not "unused variable". */
+#define _raw_read_lock(lock)	(void)(lock)
 #define _raw_read_unlock(lock)	do { } while(0)
-#define _raw_write_lock(lock)	(void)(lock) /* Not "unused variable". */
+#define _raw_write_lock(lock)	(void)(lock)
 #define _raw_write_unlock(lock)	do { } while(0)
 
 #endif /* !SMP */
 
-#ifdef CONFIG_PREEMPT
-
+/*
+ * Define the various spin_lock and rw_lock methods.  Note we define these
+ * regardless of whether CONFIG_SMP or CONFIG_PREEMPT are set. The various
+ * methods are defined as nops in the case they are not required.
+ */
 #define spin_lock(lock)	\
 do { \
 	preempt_disable(); \
@@ -129,31 +93,175 @@ do { \
 
 #define spin_trylock(lock)	({preempt_disable(); _raw_spin_trylock(lock) ? \
 				1 : ({preempt_enable(); 0;});})
+
 #define spin_unlock(lock) \
 do { \
 	_raw_spin_unlock(lock); \
 	preempt_enable(); \
 } while (0)
 
-#define read_lock(lock)		({preempt_disable(); _raw_read_lock(lock);})
-#define read_unlock(lock)	({_raw_read_unlock(lock); preempt_enable();})
-#define write_lock(lock)	({preempt_disable(); _raw_write_lock(lock);})
-#define write_unlock(lock)	({_raw_write_unlock(lock); preempt_enable();})
+#define read_lock(lock)	\
+do { \
+	preempt_disable(); \
+	_raw_read_lock(lock); \
+} while(0)
+
+#define read_unlock(lock) \
+do { \
+	_raw_read_unlock(lock); \
+	preempt_enable(); \
+} while(0)
+
+#define write_lock(lock) \
+do { \
+	preempt_disable(); \
+	_raw_write_lock(lock); \
+} while(0)
+
+#define write_unlock(lock) \
+do { \
+	_raw_write_unlock(lock); \
+	preempt_enable(); \
+} while(0)
+
 #define write_trylock(lock)	({preempt_disable();_raw_write_trylock(lock) ? \
 				1 : ({preempt_enable(); 0;});})
 
-#else
+#define spin_lock_irqsave(lock, flags) \
+do { \
+	local_irq_save(flags); \
+	preempt_disable(); \
+	_raw_spin_lock(lock); \
+} while (0)
 
-#define spin_lock(lock)			_raw_spin_lock(lock)
-#define spin_trylock(lock)		_raw_spin_trylock(lock)
-#define spin_unlock(lock)		_raw_spin_unlock(lock)
+#define spin_lock_irq(lock) \
+do { \
+	local_irq_disable(); \
+	preempt_disable(); \
+	_raw_spin_lock(lock); \
+} while (0)
 
-#define read_lock(lock)			_raw_read_lock(lock)
-#define read_unlock(lock)		_raw_read_unlock(lock)
-#define write_lock(lock)		_raw_write_lock(lock)
-#define write_unlock(lock)		_raw_write_unlock(lock)
-#define write_trylock(lock)		_raw_write_trylock(lock)
-#endif
+#define spin_lock_bh(lock) \
+do { \
+	local_bh_disable(); \
+	preempt_disable(); \
+	_raw_spin_lock(lock); \
+} while (0)
+
+#define read_lock_irqsave(lock, flags) \
+do { \
+	local_irq_save(flags); \
+	preempt_disable(); \
+	_raw_read_lock(lock); \
+} while (0)
+
+#define read_lock_irq(lock) \
+do { \
+	local_irq_disable(); \
+	preempt_disable(); \
+	_raw_read_lock(lock); \
+} while (0)
+
+#define read_lock_bh(lock) \
+do { \
+	local_bh_disable(); \
+	preempt_disable(); \
+	_raw_read_lock(lock); \
+} while (0)
+
+#define write_lock_irqsave(lock, flags) \
+do { \
+	local_irq_save(flags); \
+	preempt_disable(); \
+	_raw_write_lock(lock); \
+} while (0)
+
+#define write_lock_irq(lock) \
+do { \
+	local_irq_disable(); \
+	preempt_disable(); \
+	_raw_write_lock(lock); \
+} while (0)
+
+#define write_lock_bh(lock) \
+do { \
+	local_bh_disable(); \
+	preempt_disable(); \
+	_raw_write_lock(lock); \
+} while (0)
+
+#define spin_unlock_irqrestore(lock, flags) \
+do { \
+	_raw_spin_unlock(lock); \
+	local_irq_restore(flags); \
+	preempt_enable(); \
+} while (0)
+
+#define _raw_spin_unlock_irqrestore(lock, flags) \
+do { \
+	_raw_spin_unlock(lock); \
+	local_irq_restore(flags); \
+} while (0)
+
+#define spin_unlock_irq(lock) \
+do { \
+	_raw_spin_unlock(lock); \
+	local_irq_enable(); \
+	preempt_enable(); \
+} while (0)
+
+#define spin_unlock_bh(lock) \
+do { \
+	_raw_spin_unlock(lock); \
+	preempt_enable(); \
+	local_bh_enable(); \
+} while (0)
+
+#define read_unlock_irqrestore(lock, flags) \
+do { \
+	_raw_read_unlock(lock); \
+	local_irq_restore(flags); \
+	preempt_enable(); \
+} while (0)
+
+#define read_unlock_irq(lock) \
+do { \
+	_raw_read_unlock(lock); \
+	local_irq_enable(); \
+	preempt_enable(); \
+} while (0)
+
+#define read_unlock_bh(lock) \
+do { \
+	_raw_read_unlock(lock); \
+	preempt_enable(); \
+	local_bh_enable(); \
+} while (0)
+
+#define write_unlock_irqrestore(lock, flags) \
+do { \
+	_raw_write_unlock(lock); \
+	local_irq_restore(flags); \
+	preempt_enable(); \
+} while (0)
+
+#define write_unlock_irq(lock) \
+do { \
+	_raw_write_unlock(lock); \
+	local_irq_enable(); \
+	preempt_enable(); \
+} while (0)
+
+#define write_unlock_bh(lock) \
+do { \
+	_raw_write_unlock(lock); \
+	preempt_enable(); \
+	local_bh_enable(); \
+} while (0)
+
+#define spin_trylock_bh(lock)	({ local_bh_disable(); preempt_disable(); \
+				_raw_spin_trylock(lock) ? 1 : \
+				({preempt_enable(); local_bh_enable(); 0;});})
 
 /* "lock on reference count zero" */
 #ifndef ATOMIC_DEC_AND_LOCK